容易获得良好焊缝成型的焊接位置是（）。
A.平焊位置
B.立焊位置
C.横焊位置
D.仰焊位置
参考答案：A
根据句意，用所给单词的适当形式填空。
1. Look, there is a bird _____ (sing) in the tree.
2. The bad air makes my chest hurt and it's difficult for me _____ (breath).
3. They are doing their homework carefully. You'd better not _____ (disturb) them.
4. Litter _____ (influence) the look of our city.
5. It is known that smoking does great _____ (harm) to us.
协同是要素有利于物流系统的一种联系方式，怎样能算是达到协同？
